Electronic door opening device



June 12 1962 G. A. WEIBLE ELECTRONIC DOOR OPENING DEVICE Filed March 15, 1961 INVENTOR. GEORGE A. WEIBLE WILSON, SETTLE 8: CRAIG ATTORNEYS United States Patent ()filice Patented June 12, 1962 3,039,038 ELECTRONIC DOOR OPENING DEVICE George A. Weible, Detroit, Mich., assignor to Industrial Electronics Inc., Detroit, elm, a corporation of ichigan Filed Mar. 15, 1961, Ser. No. 95,972 7 Claims. (Cl. 318478) tional devices have comprised a plurality of Interlocking relays which operate to control a motor to open and close While such conventional devices have in general operated satisfactorily, the use of a plurality of relays has made the devices relatively expensive and the service life has been relatively short because of rapid deterioration of the relays.

and durable electronic components.

Another object of the invention is to provide a door opening device having only one relay, thus permitting the use of a high quality relay having a longer life while opening device having switches operated by pe sons approaching the doorway, the switches being low-current devices to insure the safety of the users.

Another object of the invention is to provide a door opening device with an extended service life.

Other objects of this invention will appear in the followbeing practiced or carried out in various ways. Also, it is to beunderstood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

FIGURE 1 illustrates a typical door structure 10 which is operated to open and close by means of the present invention.

depressible panels 20, 21 which operate, when stepped on, to close a switch positioned thereunder.

In operation, a person approaching the in door from the result that safety switch 24 remains open.

Power is supplied from a suitable source 26 to the primary coil 28 of transformer 30. The transformer 30 is shown as having an iron core 32. A lead 34 extends from one side of the transformer secondary coil 36 and a second set of contacts 66 which form part of the present control circuit. The rectifier 56 provides a pulsating D.C. curren to operate the coil. The function of the capacitor 50 is to smooth the ter to the transistor base 68. The emitter to base current is controlled by the approach switch 22 and a second control transistor 7 0.

lead 96 which extends from the base 98 and has a branch 100 with resistor 102 which connects with the lead 60 to 70 to conduct, permitting power transistor 44 to conduct and energize relay coil 52 to open the door.

In the above described circuit, resistor 74 acts to limit the current drawn by transistor 44, resistor 76 is a load resistor for a diode 104, the light 88 and resistor 90 form part of a test circuit, and the resistor 102is a biasing resistor for the control transistor 70. A biasing resistor 6 is connected by lead 108 from the base 68 of the power transistor 44 to the lead 34 which connects to the secondary transformer coil 36.

When relay coil 52 is energized, it will close its normally open contacts 62 and 66. Referring to FIGURE 3, the contacts 62 comprise a pair of contacts 110, 112 to provide a double break switching action. The double break reduces arcing on opening and results in less contact wear. Closing of the contacts 62 closes a circuit between leads 114, 116. Lead 114 connects to the motor 64. A lead 118 extends from the motor to a source of power 120. The lead 116 is connected to the other side of power 120. It will thus be seen that closing of contacts 62 is effective to energize the motor '64 to open the door. Other control components may be provided in this circuit to control such factors as the rate of door opening and the extent of door movemen After the door has opened, the person entering will step oif the approach mat to pass through the door opening. In so doing, he will release approach switch 22 which will immediately open. Means thus have to be provided to hold the door open for a long enough period to permit the person to walk through and off the safety mat 18. This is accomplished in two steps. First means are provided to hold the door open for a limited time with both switches 22 and 24 open. When switch 24 is closed subsequent to the closing of switch 22, second means are provided to hold the door open for as long as switch 22 is closed.

The means for holding the door open when both switches 22, 24 are open comprise an electrolytic capacitor 122 and the diode 104. Lead 124 extends from the capacitor 122 into connection with the lead 46 which eX- tends from the transistor collector 48. A second lead 126 extends from the other side of the capacitor 122 into connection with lead 72 between the resistors 7 4, '76. Lead 128 connects the diode 104 between leads 126 and 46. The function of diode 104 is to prevent application of a reverse voltage on the capacitor 122, which would cause excessive wear on the capacitor. In essence, the diode shorts out the capacitor during one half cycle. When switch 22 is opened, capacitor 122 will keep the power transistor 44 in conduction for approximately one and one-half seconds. Continued conduction by transistor 44 will keep the relay coil 52 energized and the door will remain open.

After the elapse of one and one-half seconds, transistor 44 would cease to function. However, by this time it is assumed that the person will have traveled through the door opening and will have depressed safety panel 21 to close switch 24. Closing of switch 24 will close a second path through the circuit to permit emitter to base current flow in the power transistor 44. This path comprises lead 72 from the base 68, resistors 74, 76, lead 78, from which extends lead 132 to switch 24. Lead 132 extends from the other side of the switch 24 to he relay contacts 66. In view of the fact that relay coil 52 is at this time energized, contacts 66 will be closed. Lead 134 extends from the relay contacts to parallel arranged resistor 136 and light 13 8. The resistor and light form a part of the aforementioned test circuit. Lead 60 extends from the resistor 136 and light 13 8 to the secondary coil 36 to complete the path for emitter to base current flow of the transistor 44. This path will remain closed as long as the switch 24 is closed. Thus, untilthe person steps off the safety mat, the door will remain open.

The switch 24 also acts to prevent opening of the door if a person is standing on the safety mat 18 when a second person steps onto the approach mat 16'. In this case, switch 24 will be closed before switch 22 is closed. When switch 24 is closed without the previous energization of relay coil 52, a circuit is not completed from the transistor base 68 to power because the contacts 66 of the relay will be in their normally open position. Thus, the door will not open if switch 24 is closed before closure of switch 22.

If switch 22 is closed subsequent to closure of switch 24, the door will still not open. It will be noted that a resistor is connected by lead 142 between the control transistor base 98 and lead 132. Resistor 140 is selected with a value to bias the transistor 70 to cutoff and prevent operation of this transistor. Thus, both potential paths, through transistor 70 and through relay contacts 66, are open preventing conduction by transistor 44. In view of the fact that transistor 44 must conduct before relay coil 52 will be energized, it will be appreciated that the door will not open under these circumstances.

An alternate method of operating transistor 44 is provided for the case where it is desired to permanently hold the door open. This might be desired, for example, on warm summer days. In this circuit, the base 68 is connected to power via lead 72, resistors 74, 76, lead 144,

resistor 146, lead 148, switch 150, and lead 152 which connects to lead 60 and thence to the secondary coil 36. As will be appreciated closure of switch will complete this circuit and excite the transistor 44 to cause opening of the door. The door will remain open until switch 150 is again opened.

A test circuit is also provided for trouble shooting the device when it fails to perform. The most frequent problem encountered in service is the shorting out of the switches 22, 24. This may occur because the switches stick in the closed position or foreign material of a conducting nature may cause such shorting. The test circuit comprises normally open test switch 154 having a contact point 156 connected to lead 34. tends from switch 154 into connection with lead 148 which, as previously mentioned, is connected to lead 78. Resistor 146 has a lo resistance. The closure of switch 154 places resistor 146 in parallel with resistors 74, 76

and 106. The net resistance of this network is relatively low, permitting the flow of a relatively high current there-- through. This current is high enough to' cause lighting of lights 88, 13 8 if the respective switches 22, 24 are closed. Such closure, could, as previously mentioned, be

due to a short or sticking of the switch.

136 are provided in parallel with the lights in order to' keep the circuits closed in the event the lights burnout.

If light 88 lights, then it may be assumed that switch 22 is shorted. If light 138 lights, then it may be assumed that switch 24 is shorted. If neither light lights, the service man may close switch 22. If the door does not open but light 88 lights, then it can be assumed that the problem is in the transistor 44 circuit. If this is the case, the field can be further narrowed by subsequently closing switch 24. If light 138 then goes on, transistor 44 and the relay are operating properly. The trouble is then in the control circuit operating the motor 64.

The door opening device of the present invention incorporates only two transistors and one relay, It is estimated that this circuit eliminates the necessity for four relays as presently used in conventional devices. The cost of a transistor is approximately one-third that of the relays used. From this, it is evident that there is a considerable cost saving in the present structure. Additionally, there is a considerable reductionin size and it has been found in practice that the present device has 'a service life of approximately 5 million cycles as compared to 50,000- 100,,000 in previous devices Another advantageous feature in the device resides in the use of a low-voltage cone quality, relatively expensive relay which will perform in the range of inclusion of such an expensive relay within the price structure of such opening devices is made possible by the cost savings-effectuated elsewhere in the system.

Lead 158 ex Having thus described my invention, I claim: tween the base of said first transistor and said first switch 1. An automatic door-opening transistor circuit comto the base of the second transistor, said biasing resistor prising first and second transistors each having a base being operative to prevent conduction by said second electrode, an emitter electrode, and a collector electrode, transistor when said second switch is closed a relay 0011 the case of the first transistor being connected to the connected between said first transistor collector and said emitter of said second transistor, a normally open switch source of power, said 0011 being energized when the first interposed between said first transistor base and said sectransistor conducts, a set of normally open relay conond transistor emitter, a source of power to excite said t acts operated to close upon energization of said coil first and second transistois to conduct when said switch and a circuit including a source of power and a dooris closed, a relay coil connected between said first transisopening motor, said relay contacts being interposed in tor collector and said source of power, said coil being said lastmentioned circuit and being operative upon energized when the first transistor conducts, a set of norclosure to cause actuation of said motor. nially open relay contacts operated to close upon energiza- 5. An automatic door-opening transistor circuit comtion of said coil and a circuit including a source of power prising first and second transistors each having a base and a door-opemng motor, said relay contacts being inelectrode, an emitter electrode, and a collector electrode ter-posed in said lastmentioned circuit and being operative the base of the first transistor being connected to the upon closure to cause actuation of said motor. emitter of said second transistor, a first normally open An automatic door-opening transistor circuit cornswitch interposed between said first transistor base and prising first and second transistors each having a base said second transistor emitter, a source of power to excite electrode, an emitter electrode, and a collector electrode, said first and second transistors to conduct when said h as 0f t first transistor being connected to the emitswitch is closed, a capacitor connected between the base ter of said second transistor, a normally open switch inand collector of the first transistor, said capacitor being terposed between said first transistor base and said second operative to cause conduction of the first transistor for a and second transistors to conduct when said switch is coil connected between said first transistor collector and closed, a capacitor connected between the base and 001- said source of power, said coil being energized when the lector of the first transistor, said capacitor being operative first transistor conducts, first and second sets of normally to cause conduction of the first transistor for a period of open relay contacts opei ated to close upon energization time after opening of said switch, a relay coil connected of said coil a first lead extending from a point between between said first transistor collector and said source of the base of the first transistor and said first switch to to close upon energization of said 0011, and a circuit inin the first lead between the second set of relay contacts eluding a source of power and a door-opening motor, said land the base of the first transistor, a second lead extendrelay contacts being interposed in said lastmentioned ciri'ng from the first lead from a point between said second cuit and being operative upon closure to cause actuation switch and the second set of relay contacts into connection of said motor. with the base of the second transistor, a biasing resistor 33. An automatic door-opening transistor circuit cominterposed in said second lead closure of said second electrode, an emitter electrode, and a collector electrode, 40 operative to continue conduction of said first transistor,

the base of the first transistor being connected to the emitclosure of said second switch prior to energization of ter of said second transistor, a first normally open switch the relay coil being operative, via said biasing resistor interposed between said first transistor base an sai secto prevent conduction of said second transistor, whereby first and second transistors to conduct when said first is closed prior to closure of said second switch, and a switch is closed, a relay coil connected between said first circuit including a source of power and a door-opening and second sets of normally open relay contacts operated t use actuation of said motor, to close upon energization of said coil, the base of the first 6. A devic as claimed in claim 5 and further char c- Of the relay C0i1 being operative t Continue Conduction first transistor to conduct to energize said relay coil.

motoT- erated signalling device in series with said second norprising first and second transistors each having a base emitter of said second transistor, a first normally open a biasing resistor connected in series from a point be- No references cited. 

